Al-Ti-C grain refiners form a relatively new alternative to the existing class of Al-Ti-B type grain refiners for achieving fine equiaxed structures in aluminum alloys during casting and solidification. The present study was carried out to investigate the influence of Al-Ti-C master alloys on the grain size of high purity aluminum and hypoeutectic Al-Si alloys. It is well known that typical alloying elements affect significantly the grain refining performance in hypoeutectic Al-Si alloys. This study investigates the relationship between grain refining efficiency and concentrations of Fe and Si in aluminum alloys. It has been found that grain reflnement was successful when using small addition of Al-3 wt, ％Ti-0.15.wt.％C master alloy(0.006wt. ％ Ti addition levels) in hypoeutectic Al-Si alloys. Furthermore, several factors such as holding time, alloy composition, pouring and temperature had an influence on the grain refinement performance.